FILAR CYST

Defintion

• Anechoic, cystic structure completely contained within the filum terminale
• Filum terminale- fibrous tissue proceeding downward from the conus medullaris

PATIENT HISTORY

• 6 weeks old
• Presented with sacral dimple
• Labs: No known abnormal values

Sacral Dimple

SCANNING TECHNIQUE

• 9 MHz linear transducer
• Patient is prone
• Transverse and saggital imaging plane

Saggital/Transverse
Filar Cyst
(without measurements)

Saggital/Transverse
Filar Cyst
(with measurements)

DIAGNOSIS

• Small incidental filar cyst measuring up to 8mm in length, 2 mm in diameter
• No filar thickening
• Filum appears more tight than expected

SUMMARY

• After saggital and transverse scan planes of the lumbar and sacral spine, a filar cyst was seen at the level of L3
• Benign, normal variant
• No treatment or follow up requested

Differential diagnosis

• Ventriculus Terminalis (aka 5th ventricle)
• Fluid-filled cyst within spinal canal
• Inside the conus medullaris
• Continuity between cyst and central canal of spinal cord

Differential diagnosis

• Ventriculus Terminalis (aka 5th ventricle)
• Fluid-filled cyst within spinal canal
• Inside the conus medullaris
• Continuity between cyst and central canal of spinal cord

Differential diagnosis

• Syringomyelia
• Fluid-filled cyst within spinal canal
• Caused by protrusion of brain tissue into spinal canal
• Blocks CSF circulation

Resources


Sacral dimple. (2012, October 24). Retrieved June 16, 2015, from http://www.mayoclinic.org/diseases-conditions/sacral-dimple/basics/definiti...


Youssef, A., Bellussi, F., Rizzo, N., Pilu, G., & Ghi, T. (2013, August 13). Cyst of the filum terminale: Two cases detected on prenatal ultrasound. Retrieved June 16, 2015, fromhttp://onlinelibrary.wiley.com/store/10.1002/uog.12524/asset/uog12524.pdf;jsessi...